let me just throw this out there ... wouldnt insulation also just hold the heat in???

release of heat at night is as important as trying to avoid heat accumulation during the day ...

i would probably do pot in pot.. and have many pots.. so i could switch them out every other day or so ... and i would have these decorative wooden planters in full bright shade.. to avoid day heat ....

also.. you dont mention size .. but if i were working my theory.. size would be dictated by the size of the nursery pots i could get... so they fit in nicely ... and are easy to remove..

and never forget .. the most important thing in a pot.. is the media .. not the pot.. not the plant .. and not the planter ... you can probably cool the media in the evening with a good well draining drenching ...

in other words.. the planter itself would be the last variable ... and its design would not dictate any of the remainder ...

i know nothing about AZ plants nor weather.. but thats my 2 cents .. and that and a shiny nickle gets you 7 cents.. good luck ..

ken

Skip the insulation - calling for trouble. It may retard heat gain but if the pot becomes hot and it will, then it will also retard heat loss. Paint your planter white and it will reflect Sunlight and reduce a lot of the heat gained by the planter. If you want you can use an insulator on the side facing the Sun but keep the other side un-insulated. If you can use a clay pot - it will cool by evaporation of water. But also means it will dry out faster.

Filling the outer planter with shredded mulch and keeping it wet is also very effective. I protect my small pots this way. I have home made wood boxes with small pots embedded in the mulch. Water retards heat gain (and loss too) a lot. Although we do not ever get as hot as you do.

There are other complex solutions: An automatic mid-day misting system to keep the plants cool. A 50% shade cloth stretched across your planting area is commonly used by greenhouses and nurseries.

Thank you Ken and Mary for your suggestions!

Ken: I admit I don't know much about insulation or thermodynamics. But one of the few things I remember being taught on the subject is that heat rises, just as we lose most of our heat through our heads. So I'm hoping that heat would be able to dissipate out the top of the container. But I could be wrong, which is why I posed these questions ;).

I use a mix of 5 parts pine bark fines and 1 part perlite, no peat at all. I don't think I can get anything to drain much faster than that, unless I were to use a gritty mix. And I still ran into overwatering issues when I tried watering daily. It's over 100 degrees out there and I still have to space my watering out several days or I get yellowing leaf drop. I believe my container is too big for my tree, and with the high temps my roots aren't as efficient drinking the water.

Mary: The insulating blankets is a good idea. I also like the frozen water bottles. I actually put some in the freezer last night to try today, I just have to figure out how to place them in my current set up, which is the single pot. I am thinking I will just lay them on the top and try to bury them a bit underneath the existing mulch covering. We'll see if it helps. Actually embedding them in the potting mix would probably be more effective but would also be a pain to switch out every day. I'm also testing wrapping my container in soaked towels to see if I can harness evaporative cooling.

Something's gotta work, right?!

Have you thought about using olla's for watering? It may not be feasible with your pot because they need a lot of room. I've used olla's in the past and was pleased with the result. Buying one like in the link below is very expensive but, back to Goodwill, I often found those clay wine cooler thingies worked great and were cheap. Cover them with a clay pot saucer. Here's a link in case you have no idea what I'm talking about. :-)

Using olla's in the garden

The wood itself is an insulator. Were you going to paint them?

tj

That's an interesting idea Mary, it's a new concept to me. I'm having a hard time visualizing how to adapt that to a container tree, though. Wouldn't the root ball displace the olla? Or are you thinking I could put a small one off-center? Would that cause all my roots to grow to that side, instead of spreading out and down?

TJ: The wood would certainly provide shade for an interior pot, but don't you need "dead air" or something like that to provide insulation? There would be plenty of space between the exterior wood and the interior pot for warm air to circulate.

I hadn't decided on painting them. I generally like wood grain, but painting them white or another light color could help reflect heat away.

The cells in the wood provide the air space. If you want more then line the planter with bubble wrap and fill them with potting soil and either plant directly or sink a pot in the mix.

tj

Travis, Yes, the olla would be hard to do with a container and you're right, the roots would grow towards the olla. I just like the whole olla concept but it won't work for your current problem.

Thanks tropicofcancer, you're not the first to suggest that increasing my insulation will also make it harder for the pot to cool, so that tells me it's something I need to pay attention too. Given my location, I probably will paint them white. May not be my aesthetic choice but will be more helpful to the plants.

https://www.eyeofthedaygdc.com/2018/02/the-history-of-versailles-citrus-planter-boxes/

My soil temperature is 6F cooler than ambient temperature today because the clay cools the soil when water evaporates from the clay. The clay loses so much water through evaporations I had to water twice today.

That's a cool device you have there Lemon Lime Orange! That takes the guess work out of things :)

I keep hearing about how clay pots lose so much water but that hasn't been my experience. I'm using fairly large unsealed terra cotta. I know it's porous because the outside of the pots crust over from the residue of evaporated water. Yet, in successive days of dry, triple digit temperatures and a bark/perlite (no peat) mix, I am overwatering my meyer lemon even if I water 1x every 2-3 days. I just went about 1 week to allow my medium to dry out a few inches down.

I read on these forums where people talk about having to water every day or multiple times per day in the hot summer but I just don't get it. The only thing I can think of is that my pots are too big for the young trees.

Other answers above are good, but just thought I'd correct this common misconception:

" I admit I don't know much about insulation or thermodynamics. But one of the few things I remember being taught on the subject is that heat rises, just as we lose most of our heat through our heads. So I'm hoping that heat would be able to dissipate out the top of the container. But I could be wrong, which is why I posed these questions ;)."

Yeah, no. Try to wipe out the incorrect "heat rises" from your memory and replace it with "hot air or fluid rises." Unfortunately the wrong phrase is easy and sticks in all our memories. It is only with a fluid or gas, that the warmer portion rises above the cooler portion, which is called convection. All other forms of heat transfer do not prefer upward movement.

Losing heat through the head is unrelated.

https://youtu.be/E0lFyE-IDX4

The Blue Lab Pulse meter has made it super easy to know when to fertilize. Without the meter I would chronically over-fertilize. Nothing kills citrus faster than too much NPK. I use a sphagnum peat moss based potting soil. It has always worked really well for me indoors and out.

The original Versailles Citrus Planters had removable sides. They designed them that way so that they could trim the roots.

Hi Travis, here is a great idea for shading your citrus. See 5 minutes into the video.

https://www.youtube.com/watch?v=jkAKY0Gic3E

Thanks LLO. That looks especially helpful if you are planting in ground.

If the container is on concrete just fold the fabric under the bottom and place container on top of the fabric. Shade cloth, wire mesh, and ties are all stock items at home depot.

https://www.homedepot.com/p/6-ft-x-20-ft-Sun-Screen-Fabric-Shade-Canopy-in-Chocolate-Heavy-Duty-81020R/204631818